Method for creating a channel through a foreign material

ABSTRACT

A method for creating a channel through a foreign material located in a body of a patient, the foreign material defining a material first surface and a substantially opposed material second surface, the channel extending through the foreign material between the material first and second surfaces, the method using an apparatus including a substantially elongated member defining a proximal end region and a substantially longitudinally opposed distal end region, the apparatus including an electrode located about the distal end region, the method comprising: introducing the distal end region into the body of the patient; positioning the electrode substantially adjacent to the material first surface; energizing the electrode with a radiofrequency current; and using the electrode energized with the radiofrequency current to deliver energy into the foreign material to create the channel.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional application No. 60/827,446, filed on Sep. 29, 2006 incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to methods and devices usable to deliver energy within the body of a patient. More specifically, the present invention is concerned with a method for creating a channel through a foreign material.

BACKGROUND OF THE INVENTION

There are many situations in which it would be desirable to create a channel through a foreign material located in a body of a patient. For example, the following two papers give examples of such procedures: McWilliams et al., “In Situ Stent-Graft Fenestration to Preserve the Left Subclavian Artery” Journal of Endovascular Therapy Vol. 11, No. 2, pp. 170-174; and McWilliams et al. “Retrograde Fenestration of Endoluminal Grafts From Target Vessels: Feasibility, Technique, and Potential Usage.” Journal of Endovascular Therapy: Vol. 10, No. 5, pp. 946-952, the contents of which are incorporated herein by reference in their entirety.

In some cases, a graft composed of foreign material including a substantially tubular supporting structure, for example a stent, needs to be positioned within a vessel of the body of the patient. However, because of the configuration of the vessel, side branches extending from the vessel may be obstructed by the graft. Restoration of flow through these side branches is relatively difficult to perform with a percutaneous needle because of the relatively large forces required. Also, the relatively large forces exerted onto the needle create a risk that the needle will pass through the foreign material suddenly and damage adjacent tissues.

Radiofrequency (RF) perforation is usable to create channels through biological tissues. It is commonly understood, as stated for example in Shimko et al., “Radio frequency perforation of cardiac tissue: modeling, and experimental results”, Med Biol. Eng. Comput. 38 pp. 575-582 (2000), that in this method, the RF energy serves to rapidly increase tissue temperature to the extent that water in the intracellular fluid becomes converted to steam, inducing cell lysis as a result of elevated pressure within the cell. Furthermore, electrical breakdown may occur within the cell, wherein the electric field induced by the alternating current exceeds the threshold dielectric strength of the medium located between the radiofrequency perforator and the cell, causing a dielectric breakdown. In addition, mechanical breakdown may occur, wherein alternating current induces stresses on polar molecules in the cell. Upon the occurrence of cell lysis and rupture; a void is created, allowing the device to advance into the tissue with little resistance. Since foreign materials are not made out entirely, or at all, of cellular-based biological tissue, this mechanism seems unlikely to work in such materials.

Against this background, there exists a need in the industry to provide a novel method for creating a channel through a foreign material. An object of the present invention is therefore to provide a method for creating a channel through a foreign material.

SUMMARY OF THE INVENTION

In contrast to the commonly understood mechanisms of radiofrequency perforation, it has been unexpectedly found that, as described further herein below, a radiofrequency-based apparatus is usable to create channels through foreign materials which may be, for example, substantially synthetic materials.

In a first broad aspect, the invention provides a method for creating a channel through a foreign material located in a body of a patient, the foreign material defining a material first surface and a substantially opposed material second surface, the channel extending through the foreign material between the material first and second surfaces, the method using an apparatus including a substantially elongated member defining a proximal end region and a substantially longitudinally opposed distal end region, the apparatus including an electrode located about the distal end region, the method comprising:

-   -   introducing the distal end region into the body of the patient;     -   positioning the electrode substantially adjacent to the material         first surface;     -   energizing the electrode with a radiofrequency current; and     -   using the electrode energized with the radiofrequency current to         deliver energy into the foreign material to create the channel.

Examples of such foreign materials include any cellular-based material (in addition to biological tissue), as well as any synthetic material that absorbs water or that will melt at the operating temperature of the electrode. For example, and non-limitingly, the foreign material has a melting temperature of less than about 150 degrees Celsius.

Advantageously, the proposed method allows an intended user to relatively easily create the channel using an apparatus that has been advanced through a relatively tortuous path through the body of the patient, as minimal force is required be exerted onto the material with the distal end region of the apparatus in order to create the channel.

In some embodiments of the invention, the proposed method is performed using a sequence of a relatively small number of relatively quick and ergonomic steps using devices substantially similar to existing radiofrequency perforation apparatuses.

In addition, the proposed method is relatively safe for biological tissues adjacent to the foreign material, which minimizes risks of injuring these biological tissues and of creating potentially life-threatening situations.

In some embodiments, the foreign material is included in a septal patch extending across an aperture formed in the septum of the heart of a patient. In other embodiments, the foreign material is included in a stent graft occluding the ostium of a blood vessel.

Other objects, advantages and features of the present invention will become more apparent upon reading of the following non-restrictive description of preferred embodiments thereof, given by way of example only with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the appended drawings:

FIG. 1A, in a perspective view, illustrates an apparatus for creating a channel through a foreign material in accordance with an embodiment of the present invention;

FIG. 1B, in a front cross-sectional view taken along the line 1B-1B of FIG. 1A, illustrates the apparatus of FIG. 1A;

FIG. 2, in a partial perspective view, illustrates a distal end region of the apparatus of FIG. 1A;

FIG. 3A, in a partial perspective view, illustrates an embodiment of a handle usable with the apparatus illustrated in FIGS. 1A to 2;

FIG. 3B, in a side cross-sectional view, illustrates the handle of FIG. 3A;

FIGS. 3C and 3D, in perspective views, illustrate an embodiment of a securing component usable with the handle shown in FIGS. 3A and 3B;

FIG. 4, in a flow chart, illustrates a method for creating a channel in a foreign material in accordance with an embodiment of the present invention;

FIGS. 5A and 5B, in schematic views, illustrate a method for creating a channel in a septal patch extending across an aperture formed in the heart of a patient in accordance with an embodiment of the present invention;

FIGS. 6A and 6B, in schematic views, illustrate a method for creating a channel in a stent graft extending across an ostium of a renal artery of a patient in accordance with an embodiment of the present invention; and

FIGS. 7A and 7B, in schematic views, illustrate a method for creating a channel in a stent graft extending across an ostium of a renal artery of a patient in accordance with an alternative embodiment of the present invention.

DETAILED DESCRIPTION

Generally speaking, the proposed method is performed for creating a channel through a foreign material located in a body of a patient. The foreign material defines a material first surface and a substantially opposed material second surface and the channel extends through the foreign material between the material first and second surfaces. Typically, the method uses an apparatus including a substantially elongated member defining a proximal end region and a substantially longitudinally opposed distal end region, the substantially elongated member including an electrode located about the distal end region.

The method includes introducing the distal end region into the body of the patient; positioning the electrode substantially adjacent to the material first surface; energizing the electrode with a radiofrequency current; and using the electrode energized with the radiofrequency current to deliver energy into the foreign material to create the channel.

For example, the method is usable for restoring blood flow to a blood vessel of a body of a human or animal, the blood vessel being occluded by a foreign material. In this case, the channel is created through the foreign material.

As a feature of the aforementioned aspects, in some embodiments of the invention, the apparatus has a substantially atraumatic distal end, thus reducing the risk of unintentional perforation of a body vessel or other tissues. Also, the use of energy in creating the channel allows for the creation of channels in foreign materials through which creation of such channels is difficult, if not impossible, to perform using mechanical force. In some embodiments, the method is performed using relatively small apparatuses, for example apparatuses having a relatively small diameter, which are therefore relatively easily introduced into relatively small vessels.

With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the present invention only, and that many alternative embodiments of the invention are within the scope of the appended claims.

For the purposes of this description, the term ‘proximal’ indicates next to or nearer to the user, and the term ‘distal’ indicates further away from the user, when the apparatus is in use.

Apparatus

Structure

As illustrated in FIG. 1, one embodiment of an apparatus 100 according to the present invention includes a substantially elongated member 102 defining a distal end region 104 and a proximal end region 106. The distal end region 104 includes a distal tip 108 and an electrode 110 located about the distal end region 104. The electrode 110 is usable as a radiofrequency energy delivery component. In the embodiment shown in FIG. 1, the apparatus 100 further comprises an actuator 112 for directing at least a portion of the distal end region 104 in a desired direction.

The elongated member 102 may be electrically conductive and may be operable to conduct electrical energy to the distal tip 108, and more specifically to the electrode 110. In such embodiments, the elongated member 102 is also known as a core wire. In the illustrated embodiments, the elongated member 102 is at least partially covered with an insulating material 114 for substantially preventing conduction of electrical energy to surrounding bodily tissue. In accordance with these embodiments, the insulating material 114 may be made of any of a variety of electrically insulating materials and may have any suitable thickness, provided that the elongated member 102 is at least partially electrically insulated. In one particular embodiment, the insulating material 114 is at least about 0.1 mm thick. The elongated member 102 may comprise a wire that is narrow enough to be navigated through a blood vessel. In some specific embodiments, the elongated member 102 measures about 0.2 mm to about 1.0 mm in diameter.

In alternative embodiments, the insulating material 114 is discontinuous at one or more locations along the elongated member 102. For example, in one such embodiment, a number of discontinuities in the insulating material 114, along the length of the elongated member 102, create a ‘banded’ appearance, wherein insulated regions are interleaved between electrically exposed and conductive regions. In another embodiment, a region of the insulating material 114 does not completely circumscribe the elongated member 102. For example, insulating material 114 may traverse approximately 180 degrees of the circumference of the elongated member 102, leaving the remaining area electrically exposed. Any shape or pattern of discontinuities may be present and the invention is not intended to be limited in this regard. Discontinuities in the insulating material 114 may affect the distribution of energy, for example current density, around the elongated member 102 when the elongated member 102 is used to deliver energy. Embodiments of the present invention comprising such discontinuities may be suitable for specific applications, for example, when it is desirable to deliver energy along a portion of the length of the elongated member 102 or to focus the delivery of energy to a particular location or target site: In some embodiments, discontinuities in the insulating material 114 correspond, at least in part, to discontinuities in the structure of the elongated member 102. For example, in one specific embodiment, notches, described in greater detail below, are present in the elongated member 102, the thickness of the insulating material 114 being reduced in the vicinity of the notches.

In some embodiments, at least a portion of the proximal end region 106 of the elongated member 102 is electrically exposed, such that the elongated member 102 may be electrically coupled to an energy source, for example using an electrical connector.

In alternative embodiments, the elongated member 102 is made out of an electrically insulating material. In such embodiments, the insulating material 114 is typically not required. For example, in some embodiments, the elongated member 102 is made out of nylon (e.g. Pebax), polyetheretherketone (PEEK), or polypropylene, and at least one electrode 110 is attached to the distal tip 108, the electrode 110 being electrically couplable to an energy source. In one particular embodiment, the electrode 110 is electrically coupled to the actuator 112, which itself may be made of an electrically conductive material and which may be capable of being electrically coupled to an energy source. Alternatively, one or more electrodes 110 are attached to the elongated member 102, rather than to the actuator 112.

In some embodiments, at least a portion of the distal end region 104 is structured to prevent unwanted damage to a body vasculature of a patient when the apparatus 100 is inserted therethrough. For example, as shown in FIG. 2, the distal tip 108 may have a substantially atraumatic shape, for example having a blunt or rounded edge, for preventing such damage as the apparatus 100 is maneuvered through the body vasculature. In other embodiments, the distal tip 108 may be substantially semispherical, hemispherical, spherical or flattened, or may have any other shape that is unlikely to damage tissues upon contact. Alternatively or in addition, in some embodiments, at least a portion of the distal end region 104 of the elongated member 102 has a reduced rigidity relatively to the proximal end region 106. The reduced rigidity may serve to further decrease the ability of the elongated member 102 to puncture tissue, for example the tissue of a vessel wall, with the application of mechanical force. This reduced rigidity may be achieved by, for example, by the inclusion or substitution of a different material in the manufacture of the elongated member 102, by reducing the amount of material present in at least a portion of the distal end region 104, or by reducing the diameter of the actuator 112. Material may be removed, for example, by using a latticework or other discontinuous structural framework, or alternatively by thinning the wall of a portion of the elongated member 102.

In some embodiments, as seen in FIG. 1B, the elongated member 102 defines a lumen 116, as will be described further herein below, and the wall thickness of the elongated member 102 tapers in the portion of distal end region 104 approaching the distal tip 108. For example, the elongated member 102 may taper from inside to outside, thereby maintaining a consistent outer diameter and having a changing inner diameter. Alternatively, the elongated member 102 may taper from outside to inside, thereby maintaining a consistent inner diameter and having a changing outer diameter, or from both the inside and the outside thereby having the outer diameter decrease and the inner diameter increase.

As has been mentioned above, the apparatus 100, as shown in the illustrated embodiments, includes an electrode 110 located about the distal end region 104. The electrode 110 may be integral with one or both of the elongated member 102 and the actuator 112 or may be otherwise attached to the distal tip 108. For example, the distal tip 108 may, be covered with an electrically conductive cap, the cap thus forming the electrode 110. In embodiments wherein the electrode 110 is not integral with one or both of the elongated member 102 and actuator 112, the electrode 110 may be otherwise electrically coupled to one or both of the elongated member 102 and actuator 112 or to another wire operable to electrically couple electrode 110 to an energy source. For example, in one embodiment, the electrode 110 is integral with the actuator 112 and may be associated with the distal tip 108 by being passed through the elongated member 102. Alternatively, when the apparatus 100 comprises a core wire, as described hereinabove, the electrode 110 may be integral with the core wire.

The electrode 110 may be larger or smaller, or may have the same diameter, as the distal tip 108. In some embodiments, the electrode 110 is sized to be operable to generate sufficient heat to create the channel in the foreign material, when energy is supplied to the electrode at a sufficient power level. In the context of the present invention, the term foreign material encompasses any material foreign to the body being treated including synthetic materials. In one specific embodiment, the electrode may measure from about 0.40 mm to about 0.43 mm in diameter and from about 1.2 mm to about 1.5 mm in length.

In the embodiment shown in FIG. 1B, as has been mentioned above, the elongated member 102 defines a lumen 116 extending at least partially therethrough. FIG. 1B shows one embodiment of a centrally located substantially circular lumen 116 defined by the elongated member 102. In alternative embodiments, the lumen 116 has any other suitable alternative shape and size and may be eccentrically located through the elongated member 102. In other embodiments that do not comprise the lumen 116, the elongated member 102 is a substantially solid structure. The lumen 116 may be sized to receive the actuator 112 therein, as shown in FIG. 1. For example, in some embodiments, the lumen 116 is large enough to receive the actuator 112, but is not large enough to accommodate other wires, sensors, or the passage of fluid. In further embodiments, the lumen 116 is sized to receive the actuator 112 along with one or more wires but is still not be large enough to accommodate fluid flow. In one specific embodiment, the lumen 116 measures about 0.1 mm to about 1.0 mm in diameter. The flexibility of the elongated member 102 may be dependent, in part, on the wall thickness of the elongated member 102, between an inner diameter defined by the lumen 116 and an outer diameter. In one particular embodiment, the elongated member 102 has a wall thickness measuring about 0.01 mm to about 0.2 mm. The flexibility of the elongated member 102 is also dependant on the outer diameter of the elongated member 102. In some embodiments, the elongated member 102 has a beam strength of at least 0.001 lbf as measured by the ASTM E855-90 3-point bent test.

In the embodiment illustrated in FIGS. 1A, 1B and 2, the actuator 112 is operable to direct at least a portion of the distal end region 104 in a desired direction. In one embodiment, the actuator 112 comprises a single pull-wire disposed within the lumen 116 of the elongated member 102 and attached to at least one point in the distal end region 104 of the elongated member 102. For example, the actuator 112 may be attached to the distal end region 104 at or adjacent to the distal tip 108. The actuator 112 may be relatively thin, in some embodiments, in order to allow the inner diameter of the elongated member 102 to be reduced, thus potentially reducing the diameter of the apparatus 100 as a whole. In one particular embodiment, the actuator 112 measures from about 0.03 mm to about 0.30 mm in diameter.

The actuator 112 may be attached to the elongated member 102 such that manipulation of the actuator 112 via the application of mechanical energy to transmit tension along the length of the actuator 112 may effect a change in the elongated member 102. For example, in some embodiments, manipulation of the actuator 112 may cause at least a portion of the elongated member 102 to change shape. Such a change of shape may involve the adoption of a bent configuration, wherein, the term “bent” is defined to mean having a deviation from a straight line; this may take the form of a rigid bend or a subtler curve, with one or more angles of curvature. In other embodiments, this change of shape may involve a compression, or accordion-like collapsing of the elongated member 102, wherein one or more sections of the elongated member 102 fold or bend backwards. Such an effect may cause the position of the distal tip 108 to change, without necessarily inducing any deviation of the distal tip 108 away from the longitudinal axis of the distal end region 104 (i.e. the distal tip 108 may still point in its original direction).

In other embodiments of the present invention, the apparatus 100 may comprise other means for directing at least a portion of the distal end region 104 in a desired direction. For example, the apparatus 100 may comprise one or more electromagnetic, piezoelectric or hydraulic mechanisms for changing the shape of the elongated member 102. In one such embodiment, the apparatus 100 may comprise at least one magnetically responsive element, which may assist in guiding the apparatus 100 to a desired direction upon the application of a magnetic field.

In some embodiments, the apparatus 100 includes a pre-formed curved section. In such embodiments, the distal tip 108 may be directed in a desired direction by applying torque to the proximal end region 106. In such embodiments, an actuator may not be required.

With respect now to the embodiment shown in FIG. 2, the distal end region 104 of the elongated member 102 may contain one or more notches 200 to aid in a change of shape of the elongated member 102 when tension is applied through the actuator 112. For the purposes of this description, the notches 200 may be any regions wherein discontinuities are present in the wall of the elongated member 102. In some embodiments, the notches 200 comprise scores, cuts, or other discontinuities in either the inner or outer surface of the wall of the elongated member 102 that do not completely traverse the circumference of the elongated member 102. In alternative embodiments, the notches 200 comprise regions wherein entire sections of the wall of the elongated member 102 are absent. In one specific example, as shown in FIG. 2, one or more sections of the wall of the elongated member 102, each section extending at least 180 degrees around the circumference of the elongated member 102, are absent, which may result in a toothed or serrated appearance. Notches 200 are present, for example, along about 5 mm to about 50 mm of the length of the elongated member 102. The notches 200 may be regularly or irregularly spaced, identically, similarly or dissimilarly sized, oriented at any angle with respect to the elongated member 102 and may lie at any suitable angles along the elongated member 102. The notches 200 may have abrupt edges or may comprise regions where the thickness of a wall of the elongated member 102 changes gradually to create a discontinuity.

In other embodiments, the notches 200 comprise regions composed of a material different than that of the surrounding body of the elongated member 102. For example, in one embodiment, the elongated member 102 is made primarily of stainless steel while the notches 200 comprise regions of the elongated member 102 made of a different material, for example an elastic compound. The notches 200 thus represent discontinuities in the material of the wall of the elongated member 102, without necessarily changing the profile or thickness of the elongated member 102.

The notches 200 may be operable to assist in directing a change in shape of the elongated member 102 when a force is applied to the elongated member 102 through an actuator 112. In one such embodiment as described above, the application of tension to the actuator 112 applies a force to an attachment point at the distal tip 108, pulling the attachment point in a proximal direction. As notches 200 may serve to locally increase the flexibility of the elongated member 102, the elongated member 102 may change shape to, for example, bend preferentially in the direction of the notches 200 when tension is applied. Thus, in some embodiments, the notches 200 may be shaped and positioned around the elongated member 102 such that the elongated member 102 will adopt a certain specific curve or series of curves when tension is applied to the actuator 112.

In some embodiments of the present invention, and referring now to FIG. 3A, apparatus 100 includes a handle 300 mechanically coupled to the proximal end region 106 of the elongated member 102. The handle 300 may be suitable for grasping and manipulating the apparatus 100, for example during insertion, positioning or guiding thereof, and may, in some embodiments, be operable to facilitate a change in shape of the elongated member 102. Referring to FIG. 3B, in some embodiments, the handle 300 comprises a housing 302, a first securing component 304 and a second securing component 306. The handle 300 may further comprise a means for connecting an energy source to one or more of the elongated member 102, the actuator 112 and any other electrical conductor operable to deliver energy to the electrode 110. For example, the handle 300 may comprise an electrical connector for connecting to an energy source. In such embodiments, the electrical connector may be coupled to handle the 300 via an electrical cable. Alternatively, as shown in FIG. 3B, the actuator 112 may extend from a proximal end of the handle 300 and may be operable to be electrically coupled to an energy source.

The first securing component 304 may be operable to secure the handle 300 to the elongated member 102, while the second securing component 306 is operable to secure the handle to the actuator 112. In the embodiment shown in FIGS. 3B to 3D, the second securing component 306 comprises a clamping apparatus operable to securely engage the actuator 112. Actuation of the handle 300 via, for example, a button 310, may effect a change in the relative positions of the first securing component 304 and the second securing component 306, thus causing the elongated member 102 and/or actuator 112 to move with respect to one another. However, actuation of the handle 300 may be achieved using any means for displacing a wire or similar component, including but not limited to one or more of a button, a knob and a switch. Actuation of the handle 300 may involve the use of mechanical (including linear, rotational and other forces) and/or electrical energy and may be accomplished remotely. In some embodiments, the handle 300 includes a ratcheting mechanism to maintain tension in the actuator 112, for example by maintaining the position of one or more of the first securing component 304 and the second securing component 306 following actuation of the handle 300. In some embodiments, the handle 300 may be removable. For example, in one such embodiment, the first and second securing components 304 and 306 are each detachable from the elongated member 102 and the actuator 112, respectively. In such embodiments, the handle 300 may further be re-attachable after having been removed. Furthermore, in such embodiments, the handle 300 may additionally comprise one or more visual markers and/or one or more locks or other fastening mechanisms to aid in the positioning and attachment of the first securing component and the second securing component 306 respectively to the elongated member 102 and the actuator 112. Such markers and/or locks may be useful to orient the direction of bending of the elongated member 102 with respect to the handle 300, and to calibrate the actuator 112 to the amount of tension already present in the actuating mechanism. In embodiments comprising an actuator 112 that utilizes means other than tension to direct apparatus 100 in a desired direction, the handle 300 may be operable to manipulate the actuator to effect the desired change in direction.

In accordance with embodiments of the present invention, any portion of the elongated member 102, the actuator 112, the notches 200, the electrode 110 or the insulating material 114 may comprise one or more markers. Such markers may include visual markers, tactile markers, radiopaque markers, radiolucent markers, or any other markers used to aid in the visualization, localization, navigation, insertion, or detection of apparatus 100. Markers may be externally applied to a component, and may be of a variety of shapes and structures; they may be raised from the surface of a component or may conform to the surface of the component; and they may be internal to a component. In some embodiments, components may be manufactured in whole or in part from materials that provide a visual or tactile distinction, thus acting themselves as markers. For example, in one embodiment, the insulating material 114 is manufactured from a radiopaque insulating material or from a material comprising radiopaque fillers. In another embodiment, one or more of the elongated member 102, the distal tip 108, the electrode 110 and the actuator 112 are plated with a radiopaque material, such as platinum or tungsten. In yet another embodiment, a radiopaque marker, such as a band, is welded or otherwise attached to, for example, the distal tip 108 or the electrode 110.

In some embodiments, as mentioned hereinabove, any or all of the lumen 116, the actuator 112 and the notches 200 may not be present in the apparatus, in order, for example, to simply the process of manufacturing the apparatus 100 and make it more cost-effective. In addition, in such embodiments, the apparatus 100 may have substantially similar mechanical properties when compared to a standard mechanical guide-wire.

In some embodiments of the present invention, the apparatus 100 further comprises one or more means for guiding the apparatus 100 within the body of the patient. For example, in one particular embodiment, the apparatus 100 further comprises an ultrasound transducer (not shown in the drawings) associated with the distal end region 104. The ultrasound transducer (not shown in the drawings) may be operable as an intra-vascular ultrasound (IVUS) device, which may assist in determining the position of the apparatus 100 within a blood vessel, for example. In such an embodiment, the ultrasound transducer (not shown in the drawings) may be electrically connected to an ultrasound generator, for example via one or both of the elongated member 102 and the actuator 112.

In another specific embodiment, the apparatus 100 further comprises at least one optical fiber (not shown in the drawings) which may be optically coupled to an optical coherence reflectometry (OCR) system (not shown in the drawings), which may also assist in determining the position of the apparatus 100 within a blood vessel, for example.

Materials

In embodiments wherein the elongated member 102 takes the form or includes an electrically conductive core wire, as described hereinabove, it may be made of a biocompatible metal or metal alloy, for example, including, but not limited to, stainless steel or nitinol. The actuator 112 may be conductive, and may, in some embodiments, have a high tensile strength, thus being able to tolerate the application of sufficient force to cause a change in shape of the elongated member 102, when a force is applied to the actuator 112. An example of a material that is suitable for the actuator 112 is nitinol. The insulating material 114 may be composed from any material capable of providing electrical insulation, including, in some embodiments, Parylene or polytetrofluoroethylene (PTFE). The insulating material 114 may be applied to the elongated member 102 by a variety of methods including, but not limited to: being overlain onto the elongated member 102 and shrunk by the application of heat, being extruded over the elongated member 102, and being sprayed or painted onto the elongated member 102 in liquid form. Suitable materials for radiopaque markers or components include, but are not limited to, high-density metals such as platinum, iridium, gold, silver, tantalum, and tungsten or their alloys, or radiopaque polymeric compounds. Although the above materials are suggested as being suitable options for the manufacture of components of the present invention, the list is by no means meant to be limiting, and any other components with suitable properties may be used.

Method

In some embodiments, the apparatus 100 is usable to create a channel in a foreign material located the body of a patient (not shown in the drawings). This channel may be created, in some embodiments, at least partially by the delivery of energy using the electrode 110. More specifically, the electrode 110 is energized with a radiofrequency current and the electrode 110 is then used to deliver energy into the foreign material to create the channel. In some embodiments, the energy delivered in the foreign material is thermal energy.

Without being limited to a particular theory of operation, it is hypothesized that, in some embodiments, the proposed method is performed when the electrode 110, which is energized with a radiofrequency current, heats up to a predetermined temperature. For example, the predetermined temperature may be substantially larger than a melting temperature of the foreign material. Then, thermal energy is transferred from the electrode 110 to the foreign material to substantially melt the foreign material adjacent to the electrode 110, thereby creating a channel through the foreign material. In other embodiments, it is hypothesized that water may be absorbed by the foreign material, and radiofrequency energy that is thereafter delivered to the foreign material may cause vaporization of the water adjacent to the electrode 110, thereby creating a channel through the foreign material.

In some embodiments, heating of the electrode 110 is performed while the electrode 110 is positioned at a predetermined distance from the foreign material and from biological tissues adjacent to the foreign material. Positioning the electrode at a predetermined distance from the foreign material and from the biological tissues adjacent to the foreign material minimizes risks of injuring the biological tissues adjacent to the foreign material. For example, the predetermined distance is such that thermal energy transfer between the electrode 110 and either or both of the foreign material and biological tissues adjacent to the foreign material results in a non-damaging increase in temperature thereof. As mentioned hereinabove, the use of a radiofrequency current to heat the electrode 110 helps in minimizing this heat transfer, and therefore contributes to the practicality of the proposed method as the predetermined distance is then relatively small.

Minimizing injuries to tissues is of paramount importance when performing interventions in patients. Indeed, injuring a tissue typically creates stress and inflammatory responses that may cause irreversible damages to many tissues. In addition, many patients have a relatively sensitive hypothalamic-pituitary-adrenal axis (HPA axis) and local stresses to tissues can lead in these patients to systemic and psychiatric conditions and diseases. In some embodiments, the proposed method is performed in the heart of the patient. In these cases, these irreversible damages can lead to dysfunctions in the contractile and electrical conductivity properties of the cardiac tissue, which themselves can lead to life-threatening conditions.

It is hypothesized that providing the radiofrequency current to the electrode 110 within the body creates a layer of water vapor around the electrode 110, which reduces thermal transfer between the electrode 110 and adjacent structures that are sufficiently spaced apart therefrom. This helps in ensuring a relatively fast heating of the electrode 110 and reduce risks of damaging biological tissues as described hereinabove.

In such embodiments, the electrode 110 is then moved so as to be substantially adjacent to the foreign material. As the electrode has now attained a temperature substantially higher than the melting temperature of the foreign material, the electrode effectively melts the foreign material to create a channel therethrough.

However, in alternative embodiments of the invention, positioning of the electrode 110 substantially adjacent to the foreign material, for example to a first surface of the foreign material, is performed before energizing the electrode 110.

Generally speaking, the aforementioned specifics of the proposed method are typically part of a treatment procedure comprising the steps of: providing the apparatus 100, or any other suitable apparatus; inserting at least a portion of the apparatus 100 into the body of the patient, for example by introducing the distal end region into the body of the patient; positioning the electrode 110 substantially adjacent to the material first surface; energizing the electrode 110 with a radiofrequency current; and using the electrode 110 energized with the radiofrequency current to deliver energy into the foreign material to create the channel. Further embodiments may comprise additional steps of, for example, manipulating an actuator, or otherwise guiding the apparatus 100 through one or more of the body vasculature of the patient and the channel.

In accordance with embodiments of the treatment method aspects of the present invention, the apparatus 100 may be a component of a system including an energy source (not shown in the drawings) (such as, for example, the RFP-100 Baylis Medical RF Puncture Generator, manufactured by Baylis Medical Company Inc., Montreal, Canada), and a grounding pad (not shown in the drawings) or any other return electrode, if operated in a monopolar mode.

FIG. 4 illustrates, in a flow-chart form, one embodiment of a method 400 in accordance with the present invention. This embodiment comprises: at step 402, preparing a patient and a system for treatment; at step 404, inserting a portion of the apparatus 100, into the body vasculature of the patient; at step 406, navigating the apparatus 100 through the body vasculature to a target site; at step 408, changing a of shape, or otherwise reorienting the apparatus 100 in order to position the electrode 110, or any other suitable electrode, adjacent at least a portion of the foreign material; at step 410, confirming or otherwise assessing the position of the electrode 110; at step 412, delivering energy via the apparatus 100 to create a channel in the foreign material; at step 414, advancing the apparatus 100, for example the distal end region 104 and the electrode 110, through the channel; at step 416, assessing the position of the electrode 110 or any other portion of the apparatus 100 after it has been advanced through the channel; and, at step 418, performing an additional procedure at or around the target site. The reader skilled in the art will readily appreciate that the patient may be a human or an animal and that one or more of these steps may not necessarily be performed in a given procedure or that one or more of these steps may be performed in a different order, as will be further clarified hereinbelow.

In step 402, preparing a patient for treatment may include, but is not limited to one or more of: visualizing one or more treatment sites within the body of the patient using fluoroscopy, x-ray, contrast media, labeled markers such as radioactive compounds or solutions, using endoscopy procedures, using ultrasound, using Doppler imaging, or any other visualization method; characterizing the vascular system of the patient by measuring blood or serum levels of various compounds; measuring vascular pressure; and undertaking any other measuring or monitoring technique that may provide information that may be useful during any other step of the method. In step 402, preparing a system for treatment may include, but is not limited to one or more of: connecting a treatment apparatus, for example the apparatus 100 as described above, to an energy source; connecting a grounding pad or other return electrode to the energy source; placing the grounding pad or return electrode on the body of the patient; passing the actuator 112 through the elongated member 102 (in some embodiments, the actuator 112 may be permanently threaded through the elongated member 102, thus obviating this step), if the apparatus 100 comprises the actuator 112; securing the handle 300 to the actuator 112 and the elongated member 102 (in some embodiments, the handle 300 may be permanently connected to the elongated member 102 and the actuator 112, thus obviating this step); and attaching one or more additional components to the apparatus 100. As mentioned above, one or more of these steps may not be performed in a particular procedure, depending on the apparatus 100 being used and the specific procedure being performed.

The step 404 of inserting the apparatus 100 into the body vasculature of the patient may comprise percutaneously inserting the apparatus 100 into a blood vessel of the body vasculature through which the apparatus may be navigated to the target site. For example, in some embodiments, the apparatus 100 may be inserted into a femoral artery or vein or a subclavian artery or vein. The apparatus may be inserted directly into the blood vessel or may be inserted through a guiding catheter or sheath.

The step 406 of navigating the apparatus 100 through the body vasculature to a target site may involve advancing the apparatus 100 through the body vasculature to the target site. In some specific embodiments, in which the apparatus is inserted through a guiding sheath or catheter, the sheath or catheter may initially be navigated to the target site, for example by initially inserting a guidewire to the target site and then tracking the sheath/catheter over the guidewire. Once the sheath/catheter is in place, the guidewire may be removed and the apparatus 100 may be inserted through the sheath/catheter. Step 406 may additionally involve any of a variety of visualization techniques, including those techniques mentioned above for visualizing one or more treatment sites within the body of the patient. In one embodiment, the apparatus 100 may be furnished with one or more radiopaque markers, which may aid in the visualization of the apparatus 100.

The step 408 of affecting a change of shape in the apparatus 100 may be required, for example if the step of navigating the apparatus 100 does not position the apparatus 100 sufficiently precisely. This step is, in some embodiments, accomplished by effecting a change of shape in the distal end region 104 of the elongated member 102, as described hereinabove. In some embodiments, it may be desirable to approach the foreign material substantially perpendicularly, for example at an angle of about 80 degrees to about 100 degrees, and step 408 is usable to control this angle.

The step 410 of confirming a position of the apparatus 100 may involve visualizing the position of one or more portions of the apparatus 100 within the body of the patient. For example, radiopaque markers included in the apparatus 100 may be visualized using fluoroscopy. Alternatively, or in addition, radiopaque contrast may be injected, for example through the guiding sheath/catheter, in order to confirm the position of the apparatus 100. Furthermore, in some embodiments, the apparatus 100 may include a pressure sensor (not shown in the drawings) operatively coupled to the distal end region of the apparatus for measuring a pressure at or around the distal end of the apparatus. In such embodiments, blood pressure may be reassured in order to confirm the position of the apparatus.

The step 412 of delivering energy may include an optional step of measuring, assessing or sensing the composition of the foreign material to be penetrated. For example, in one embodiment, the apparatus 100 may be used as part of an impedance monitor to determine the impedance of the material to be penetrated. The impedance value thus measured may then be compared to known impedance values of various materials, in order to determine the composition of the material to be penetrated. Then, energizing the electrode 110 is performed, in some embodiments, at least in part, in a manner depending on the composition of the foreign material. For example, the electrode 110 may be energized at various power levels, depending on the nature of the foreign material. Alternatively, a change in impedance may indicate that the material in contact with the apparatus has changed. For example, a lower impedance may indicate that the apparatus is in contact with a metallic or otherwise conductive portion of a stent or scaffold, as opposed to the graft material associated with the stent/scaffold. In such a situation, a user may reposition the apparatus until a suitable impedance measurement is recorded indicating that the apparatus is substantially adjacent to the foreign material through which the channel is to be created.

Alternatively, tactile feedback may be used to assist in determining the material in contact with the apparatus. For example, a user may use tactile feedback to determine whether the apparatus is in contact with metallic material of a stent/scaffold or more flexible graft material, through which a channel may be created. Alternatively, or in addition, imaging techniques (for example OCR and/or IVUS) may be used to determine the composition of material in contact with the apparatus 100. As described hereinabove, the composition of the material to be penetrated may determine the initial parameters of energy delivery.

The step 412 of delivering energy via the apparatus 100 to create a channel in the foreign material comprises, in one embodiment, delivering electromagnetic energy (for example electric energy in the radiofrequency (RF) range) to the electrode 110. In one specific embodiment, the RF current provided may have a frequency in the range of from about 300 kHz to about 1 MHz, and more specifically, in very specific embodiments of the invention, of from about 460 kHz to about 500 kHz, and may be delivered with a power of at least about 5 W at a voltage of at least about 75 Volts (peak-to-peak).

In some embodiments, one or more parameters may be measured substantially while energy is being delivered and/or the device is being advanced. For example, impedance may be measured substantially continuously or at predetermined intervals during energy delivery and/or advancement of the apparatus and a change in impedance may lead to a change in energy delivery. In one particular example, a drop in impedance may indicate that the apparatus is contacting a metallic portion of a stent/scaffold and energy delivery may be stopped so that the device may be repositioned. The change in energy delivery may be automatic or may be manually performed by the user.

In some embodiments of the invention, the energy may be delivered for a predetermined amount of time before stopping the delivery of the energy. In other embodiments, the intended user may decide, during the course of the procedure, on the amount of time during which energy should be delivered. The intended users decision may depend, for example, on one or more of tactile feedback, impedance measurements, pressure measurements, predetermined information regarding the material being penetrated (e.g. the thickness of the material) or the preferences of the intended user. In one example, if a user feels that the device has penetrated through the foreign material he may stop delivering energy. In some embodiments, the amount of time during which energy is delivered is from about 0.1 seconds to about 5 seconds. In a more specific embodiment of the invention, the amount of time during which energy is delivered is from about 1 second to about 2 seconds. During these periods of time, the energy may be delivered continuously or as a pulsed waveform.

The step 414 of advancing the apparatus through the channel may comprise applying a longitudinal force to the proximal end region 106 of the apparatus 100 in order to advance the distal end region 104 of the apparatus 100 through the channel. Alternatively, mechanical or magnetic means for advancing the apparatus may be used. In some embodiments, step 414 occurs at least partially concurrently with step 412, such that the apparatus is advanced while energy is being delivered.

Following step 414, the position of the apparatus 100, after passing through the channel, may be confirmed at step 416. Step 416 may be performed in substantially the same manner as step 410, described hereinabove.

The step 418 of performing another treatment procedure may involve, in some embodiments, one or more of: introducing a balloon catheter, a dilator or other means for dilation of the channel, to the target site, for example overtop of or through the apparatus 100; introducing a stent or other supporting structure to the target site, for example overtop of or through the apparatus 100; delivering a pharmaceutical compound to the target site; delivering energy to create a lesion or coagulate tissue or fluid in the vicinity of the target site; introducing embolic coils; placing an IVUS or OCR probe for visualization; or adding or removing any other material to or from the site. In addition, this step may further comprise removal and possible re-attachment of the handle 300 of the apparatus 100, in order to allow for the introduction of another device to the treatment site. As mentioned hereinabove, in alternative embodiments of the invention, the electrode 110 is energized after having been positioned adjacent to the foreign material.

EXAMPLE

In a first example, an embodiment of a proposed method is used to create a channel 512, seen in FIG. 5B, within a septal patch 510 made of foreign material, the septal patch 510 defining a material first surface 514 and a substantially opposed material second surface 516. The channel 512 extends between the material first and second surfaces 514 and 516. The septal patch 510 extends across an aperture 518 defined by the septum 520 of the heart 500 of the patient, for example an atrial septum or a ventricular septum. For example, the septal patch 510 covers the aperture and extends in a plane outside of the septum 520. In other examples, the septal patch 510 extends inside the aperture 518. Some of these procedures may involve patients that have had a septal defect repaired with the septal patch 510. In some cases, such patients may suffer from one or more conditions which require access to the left side of the heart for treatment to be performed. In such situations, access to the left side of the heart may be gained by creating the channel 512 in the septal patch 510. In such embodiments, the septal patch 510 may be made of a foreign material selected from the group consisting of polyethylene terephthalate (PET, for example Dacron®), cotton, a polyester material and fabrics thereof.

With reference to FIG. 5A, the apparatus 100 is inserted through the inferior vena cava 502 into the right atrium 506 of the heart 500. In alternative embodiments, access to the right atrium may be achieved via the superior vena cava 504 as described, for example, in co-pending U.S. patent application Ser. No. 11/265,304 (Filed on Nov. 3, 2005), which is incorporated herein by reference in its entirety. FIG. 5A shows the apparatus 100 positioned in the right atrium 506 with the electrode 110 located substantially adjacent the material first surface 514. FIG. 5B shows the apparatus 100 positioned in the left atrium 508 after being advanced through the channel 512. In this particular embodiment, radiofrequency energy may be delivered, for example, at about 5 W for a period of less than about 5 seconds.

In a further example application, an embodiment of a method according to the present invention may be useful, for example, to create a channel within a graft composed of foreign material. In some embodiments, the graft is associated with a substantially tubular supporting structure, for example a stent, located within an elongated vessel of the body of the patient. In some such embodiments, the method is performed in order to restore blood flow to a branch of the elongated vessel being occluded by the graft material, thus substantially preventing fluid communication between the branch and the elongated vessel, by creating a channel through the material.

With reference now to FIGS. 6A, 6B, 7A and 7B, methods for in-situ creation of a channel through a stent-graft are illustrated. In the illustrated embodiments, a stent-graft 606, composed of a foreign material, has been placed to cover an aneurysm 604 in an abdominal aorta 600. As shown in these figures, stent-graft 606 occludes the renal arteries ostia 605.

This positioning of the stent-graft 606 is typically necessitated by an inadequate, i.e. too short, proximal neck of the abdominal aorta 600. One of the greatest challenges of stent-grafting an abdominal aortic aneurysms 604 is to obtain a long proximal attachment site to ensure a good seal without occluding the renal or supra-aortic vessels. If a long proximal site is unavailable, the ostia of the renal and/or supra-aortic vessels may become occluded by the stent-graft 606. The present invention provides a method for creating a transluminal in-situ channel in order to restore blood flow to any vessels that do become occluded during the course of such a procedure.

With reference first to FIGS. 6A and 6B, an antegrade approach to in-situ channel creation is provided. In this approach, the distal end region 104 is introduced into the body of the patient through the body vasculature inside the thoracic cavity, or in other words from a position superior to the diaphragm of the patient, and advanced towards the abdominal aorta 600 in which the electrode 110 is then positioned. FIG. 6A shows the electrode 110 of the apparatus 100 positioned in the abdominal aorta 600 substantially opposite the renal artery ostium 605, which is occluded by the stent-graft 606. At this point, energy may be delivered from an energy source through the electrode 110 in order to create a channel 608, as seen in FIG. 6B, in or through the stent-graft 606. FIG. 6B shows the electrode 110 after it has been advanced through the channel 608 into the renal artery 602. Creation of the channel allows for fluid communication and restoration of blood flow between the abdominal aorta 600 and the renal artery 602. At this point, as described above with respect to FIG. 4, the channel 608 may be dilated using one or more of a dilator and a balloon (for example a cutting balloon) and a stent may be placed across the channel 608 to maintain the patency of the renal artery 602.

With reference now to FIGS. 7A and 7B, a retrograde approach is illustrated. In this approach, introducing the distal end region 104 into the body of the patient includes introducing the distal end region into the body vasculature and through the renal artery 602 towards the abdominal aorta 600. In such an embodiment, positioning the electrode 110 substantially adjacent to a material first surface then includes positioning the electrode 110 substantially adjacent to the renal artery ostium 605 outside of the abdominal aorta 600.

With reference first to FIG. 7A, the electrode 110 of the apparatus 100 is positioned in the renal artery 602 at the renal artery ostium 605, which is occluded by the stent-graft 606. At this point, energy may be delivered from an energy source through the electrode 110 in order to create a channel 608 in or through the stent-graft 606. FIG. 7B shows the electrode 110 after it has been advanced through the channel 608 into the abdominal aorta 600. As mentioned hereinabove, creation of the channel 608 may allow for fluid communication and the restoration of blood flow between the abdominal aorta 600 and the renal artery 602. At this point, as described above with respect to FIG. 4, the channel 608 may be dilated using one or more of a dilator and a balloon (for example a cutting balloon) and a stent may be placed across the channel to maintain the potency of the renal artery. It should be noted that in the embodiment of FIGS. 7A and 7B, step 404 of the method comprises obtaining access to renal artery 602, for example during a surgical procedure or via a deep puncture.

It should be noted that, although this example has been described in conjunction with treatment of an abdominal aortic aneurysm, a similar method is also contemplated for treating a thoracic aortic aneurysm, whereby a subclavian artery, for example, may become occluded by a stent-graft. Such a condition may be more easily treated using a retrograde approach, by inserting an apparatus through the subclavian artery towards the aorta. In addition, vessels other than the renal arteries 602 may be occluded by an abdominal aortic stent-graft, for example the mesenteric arteries (not shown in the drawings). Alternatively, similar embodiments of the method may be practiced in other situations whereby a vessel ostium (or any portion of an elongated vessel, tube and/or duct) in a patient's body is occluded by a foreign material.

A method for transluminal in-situ channel formation, for example as described herein, allows for more accurate placement of the channel, less reliance on preoperative imaging, increased availability and decreased cost of a “universal”, non-customized graft, and eventually, more accessibility for a greater number of patients to the advantages of endovascular repair. As well, the technique could be used as a ‘salvage’ procedure when inadvertent coverage of side branches occurs. Most importantly, it would allow more accurate placement of the channels with the stent-graft in place in the aorta, rather than based on preoperative radiographic imaging.

The methods of the present invention provide a surprising and unexpected result in that energy, for example radiofrequency electrical energy is usable to create a channel in foreign material within the body of the patient, including, for example, synthetic material substantially not composed of cellular-based biological tissue (although it may, in some embodiments, be covered with live cells if, for example, it has been implanted in the body for a sufficient amount of time). In addition, embodiments of the present invention may minimize the risk of accidental puncture or perforation of a blood vessel or other bodily structure. Furthermore, embodiments of the present invention provide for the creation of a channel without requiring a mechanical tear of the foreign material. The methods of the present invention may also be useful in other applications, including, in general, wherever foreign material in a patient's body should be penetrated.

Many other methods and particular applications may be used with an apparatus of the present invention, and some embodiments of the method of the present invention may be used with an apparatus other than that specifically described in the “APPARATUS” section of this application.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination.

Although the present invention has been described hereinabove by way of preferred embodiments thereof, it can be modified, without departing from the scope and nature of the subject invention as defined in the appended claims. 

1. A method for creating a channel through a foreign material located in a body of a patient, said foreign material defining a material first surface and a substantially opposed material second surface, said channel extending through said foreign material between said material first and second surfaces, said method using an apparatus including a substantially elongated member defining a proximal end region and a substantially longitudinally opposed distal end region, said apparatus including an electrode located about said distal end region, said method comprising: introducing said distal end region into said body of said patient; positioning said electrode substantially adjacent to said material first surface; energizing said electrode with a radiofrequency current; and using said electrode energized with said radiofrequency current to deliver energy into said foreign material to create said channel.
 2. A method as defined in claim 1, further comprising positioning said electrode at a predetermined distance from said material first surface and from biological tissues adjacent to said foreign material prior to energizing said electrode, said positioning of said electrode substantially adjacent to said first material surface being performed by moving said electrode towards said material first surface after energizing said electrode; whereby positioning said electrode at said predetermined distance from said material first surface and from said biological tissues adjacent to said foreign material minimizes risks of injuring said biological tissues adjacent to said foreign material.
 3. A method as defined in claim 1, wherein said positioning of said electrode substantially adjacent to said material first surface is performed before energizing said electrode.
 4. A method as defined in claim 1, further comprising advancing said electrode into said foreign material towards said material second surface while delivering said energy into said foreign material.
 5. A method as defined in claim 1, wherein using said electrode energized with said radiofrequency current to deliver said energy into said foreign material to create said channel includes delivering thermal energy into said foreign material.
 6. A method as defined in claim 1, wherein energizing said electrode includes energizing said electrode until said electrode is heated up to a predetermined temperature.
 7. A method as defined in claim 7, wherein said predetermined temperature is substantially higher than a melting temperature of said foreign material.
 8. A method as defined in claim 1, further comprising assessing a composition of said foreign material.
 9. A method as defined in claim 8, wherein energizing said electrode is performed, at least in part, in a manner depending upon said composition of said foreign material.
 10. A method as defined in claim 8, wherein assessing said composition of said foreign material includes measuring an impedance of said foreign material substantially adjacent said electrode.
 11. A method as defined in claim 8, wherein assessing said composition of said foreign material includes using tactile feedback provided by said apparatus to assess said composition of said foreign material.
 12. A method as defined in claim 1, wherein said foreign material includes a synthetic material.
 13. A method as defined in claim 1, wherein said foreign material includes a material selected from the group consisting of polyethylene terephthalate (PET), cotton, a polyester material and fabrics thereof.
 14. A method as defined in claim 1, further comprising delivering said energy into said foreign material for a predetermined duration; and stopping delivery of said energy into said foreign material after said predetermined duration.
 15. A method as defined in claim 14, wherein said predetermined duration is from about 0.1 second to about 5 seconds.
 16. A method as defined in claim 15, wherein said predetermined duration is from about 1 second to about 2 seconds.
 17. A method as defined in claim 1, wherein using said electrode energized with said radio-frequency current to deliver said energy into said foreign material is performed in a manner such that said energy is delivered at a time-varying rate into said foreign material.
 18. A method as defined in claim 1, wherein energizing said electrode includes delivering said radiofrequency current to said electrode in a pulsed manner.
 19. A method as defined in claim 1, further comprising dilating said channel.
 20. A method as defined in claim 1, wherein said body of said patient includes a heart having a septum, said septum defining an aperture extending therethrough, said foreign material being included in a septal patch extending across said aperture; and using said electrode energized with said radiofrequency current to deliver said energy into said foreign material to create said channel includes delivering said energy into said septal patch.
 21. A method as defined in claim 1, wherein said body of said patient includes a body vasculature having an abdominal aorta and a renal artery branching from said abdominal aorta at a renal artery ostium; said foreign material is included in a stent graft positioned into said abdominal aorta so as to occlude said renal artery ostium; introducing said distal end region into said body of said patient includes introducing said distal end region into said body vasculature and through said renal artery towards said abdominal aorta; positioning said electrode substantially adjacent to said material first surface includes positioning said electrode substantially adjacent to said renal artery ostium outside of said abdominal aorta; and using said electrode energized with said radiofrequency current to deliver said energy into said foreign material to create said channel includes delivering said energy into said stent graft.
 22. A method as defined in claim 1, wherein said body of said patient includes a body vasculature, a thoracic cavity and an abdominal cavity, said body vasculature having an abdominal aorta located in said abdominal cavity and a renal artery branching from said abdominal aorta at a renal artery ostium; said foreign material is included in a stent graft positioned into said abdominal aorta so as to occlude said renal artery ostium; introducing said distal end region into said body of said patient includes introducing said distal end region into said body vasculature inside said thoracic cavity and advancing said distal end region towards said abdominal aorta; positioning said electrode substantially adjacent to said material first surface includes positioning said electrode substantially adjacent to said renal artery ostium inside of said abdominal aorta; and using said electrode energized with said radiofrequency current to deliver said energy into said foreign material to create said channel includes delivering said energy into said stent graft. 